IsNull.h

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/*  Copyright (C) 2008 National Institute For Space Research (INPE) - Brazil.
 
    This file is part of the TerraLib - a Framework for building GIS enabled applications.
 
    TerraLib is free software: you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation, either version 3 of the License,
    or (at your option) any later version.
 
    TerraLib is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    GNU Lesser General Public License for more details.
 
    You should have received a copy of the GNU Lesser General Public License
    along with TerraLib. See COPYING. If not, write to
    TerraLib Team at <terralib-team@terralib.org>.
 */
 
/*!
  \file terralib/dataaccess/query/IsNull.h
 
  \brief Tells if a value is NULL.
*/
 
#ifndef __TERRALIB_DATAACCESS_INTERNAL_ISNULL_H
#define __TERRALIB_DATAACCESS_INTERNAL_ISNULL_H
 
// TerraLib
#include "FunctionNames.h"
#include "UnaryFunction.h"
 
namespace te
{
  namespace da
  {
    /*!
      \class IsNull
      
      \brief Tells if a value is NULL.
 
      This function is just a syntatic-suggar.
 
      \sa UnaryFunction
    */
    class TEDATAACCESSEXPORT IsNull : public UnaryFunction
    {
      public:
 
        TE_DEFINE_VISITABLE
 
        /*!
          \brief Constructor.
 
          \param arg The argument.
 
          \note The addition operator will take the ownership of the given arguments.
        */
        IsNull(Expression* arg) : UnaryFunction(FunctionNames::sm_IsNull, arg) {}
 
        /*!
          \brief Constructor.
 
          \param arg The argument.
        */
        IsNull(const Expression& arg) : UnaryFunction(FunctionNames::sm_IsNull, arg) {}
 
        /*! \brief Copy constructor. */
        IsNull(const IsNull& rhs);
 
        /*! \brief Destructor. */
        ~IsNull() {}
 
        /*! Assignment operator.  */
        IsNull& operator=(const IsNull& rhs);
 
        /*! \brief It creates a new copy of this expression. */
        Expression* clone() const;
    };
 
  } // end namespace da
}   // end namespace te
 
#endif  // __TERRALIB_DATAACCESS_INTERNAL_ISNULL_H